Lazy loading is a technique in which elements outside the visible part of the page are loaded only once the user scrolls to them. It saves transferred data and speeds up the first render, which is a significant benefit for websites with lots of images. It has two pitfalls, though. The first is applying it to the main image at the top of the page, where the technique actually worsens perceived speed. The second is content that only loads after user interaction – clicking a button or switching a tab. A robot or a language model may never see such content, so key information such as specifications, prices, or descriptions must not be placed inside it. Check the page's source code with scripts disabled.
See also: Image optimisation, JavaScript rendering, Core Web Vitals.
